During bookbinding, the book blocks that have not yet been provided with a cover are transported by means of a transport device, while an application roller that cooperates with a scooping roller is rolled along the spine of the book block, thereby applying adhesive to the spine.
The contour of the spine of the book block can be straight or else round as well as quasi-round, which is why a correspondingly shaped application roller is used. Prior-art application rollers have, for example, a flat or profiled configuration.
These and similar methods and devices can be found in European patent application EP 0873882 A1, in German patent DE 3502733 C1 or in German patent application DE 4332069 A1.
The prior-art methods and devices call for a manual replacement of the application roller.
Whenever a new production order is received, the bookbinding line has to be brought to a standstill for safety reasons since the application roller can only be removed or installed when the housing is open. Consequently, after adhesive has been applied to the spine of the last book block belonging to the preceding production order, the machine first has to be brought to a standstill. After the housing is opened, the application roller that is currently present is removed and an application roller that is suited for the new production order is installed. In the ideal case, before the application roller that is currently present is removed, the application of glue onto the glue scooping roller is set to almost zero and consequently, the glue film thickness on the application roller is also set to the minimum thickness, so that the application roller can be removed with virtually no dripping. In order to remove the application roller, at least the side scraper, which is installed in the dismantling direction, has to be pivoted out of the way. Then the application roller is manually moved away from the glue scooping roller by means of a positioning unit and removed by hand. Subsequently, the new application roller is slid back onto the drive shaft and locked in place, and then moved towards the scooping roller by means of the positioning unit. Then the one scraper has to be pivoted back in place and both scrapers have to be adjusted to the thickness and diameter of the new glue application roller, and the glue film thickness on the glue scooping roller has to be set manually once again. Once the housing has been closed, the production can be started up again and the new production order can be processed.
The prior-art methods and devices are thus relatively time-consuming and also require manual intervention on the part of the operating personnel. As a result, especially in cases of small print runs, this translates into retooling that requires a relatively long time.
Moreover, European patent specification EP 2634007 B1 discloses a device consisting of at least two application rollers that are spaced axially relative to each other as well as a replacement apparatus for the application rollers. Each of the application rollers is oriented so as to be flush with the scooping roller. The replacement apparatus is configured in such a way that a first application roller that is oriented so as to be flush with the scooping roller can be replaced by a second application roller.
Owing to this configuration of the device and to the corresponding process sequence, the replacement of the application rollers arranged in the device can be carried out without manual intervention and independently of the size of the print run of a given production order.
However, such a solution encounters difficulties if glue residues harden on the disengaged glue application roller, since these glue residues then cause malfunctions during the subsequent use if they are not specifically removed or dissolved beforehand. These malfunctions are no longer so critical in the case of self-dissolving glue residues, if such types of glue are used.
European patent specification EP 2634008 B1 proposes using a certain automatic approach in a gluing assembly in order to switch over from one application roller to another. An installed application roller is dismantled in that, together with its rotating shaft, it is pivoted away from the glue scooping roller by using a pneumatic drive in such a way that this application roller can be swung out without touching the glue scooping roller.
The new application roller can be manually or automatically slid onto the rotating shaft, and then the above-mentioned pneumatic drive can bring this application roller back into position relative to the glue scooping roller. Because of the different round or straight contours of the application rollers, the distance has to be readjusted between the glue scooping roller and the rotating shaft—and thus the application roller.